Like many financial organizations, the UK’s government-owned savings bank, National Savings and Investments (NS&I), is choosing to move away from a reliance on legacy systems to embrace a software-as-a-service (SaaS) model.
The bank, which has long depended on rigid on-premises mainframe systems, formally announced its plan to partner with global fintech SBS, among other companies, to replace its entirely legacy core banking system. The goal is to build a platform that’s capable of delivering modern customer experiences in a way that’s secure, scalable, and resilient.
Far from being a simple vendor swap, the initiative is part of its long-term digital transformation plan, previously dubbed the Rainbow Program. While incumbent technology outsourcer Atos will mediate its partnership with SBS, NS&I will also be working with IBM for digital experience and enablement and French company Sopra Steria for customer-facing services. This strategic move to a multi-vendor model aims to reduce dependency on any one vendor, while allowing the organization to benefit from best-of-breed solutions across its various operational segments.
The new arrangement highlights the technical and operational challenges of disentangling a decades-long, deeply integrated outsourcing relationship: NS&I first outsourced its technology operations in 1999 to Siemens Business Services, which was then acquired by France-headquartered IT services provider Atos in 2011. The latest extension of that partnership comes in the wake of major global disruptions, evolving customer demands, and the growing need for more resilient operating models.
The initiative exemplifies the urgent need for change in the traditional financial services sector, not just in the UK, but the world over. A 2025 report by Cornerstone Advisors, commissioned by Alkami, found that digitally mature financial services companies can expect annual revenue growth rates of up to five times higher than their less mature peers, highlighting the immense pressure on established institutions like the NS&I to modernize.
However, there’s more to NS&I’s new digital strategy than simply improving operations and customer experiences. While the public narrative predominantly focuses on building better apps, the underlying technology is also a key foundational requirement for enhanced security and operational resilience. “De-risking” has become a central theme in the digital banking realm, especially as more sophisticated threats emerge, such as AI-generated voice clones defeating voice authentication systems and new vulnerabilities in SMS-based one-time passwords (OTPs). It’s practically impossible to upgrade a legacy banking system to effectively mitigate these new and emerging threats, hence why traditional banks like NS&I are working hard to build the foundation necessary for deploying next-generation security measures.